Future inspection microsats
The XSS-10 mission did not attract much attention from the general public. Any interest the brief mission by the military satellite could have attracted was lost in the aftermath of the Columbia accident, less than two days after the XSS-10 mission. It has, however, garnered recognition by the aerospace community: in August the mission won the AIAA’s Space Systems Technical Team Award for 2003, a prize that will be presented at the Space 2003 conference in California later this month.
The XSS-10 mission may also serve as a proof of concept for future inspection satellites, including two concepts presented during the same session of the Utah State small satellites conference as Davis’ presentation. Aaron Jacobovits of AeroAstro, a smallsat developer headquartered in Virginia, discussed his company’s Escort microsatellite. Escort, under development by AeroAstro since 1998, is designed to inspect and monitor a larger spacecraft. Escort, Jacobovits explained, could be used to check out a new GEO communications satellite, equipped with an RF payload to check the larger satellite’s antenna beams and visual and infrared cameras to check the deployment of antenna booms and solar panels. Escort would either be deployed from the larger spacecraft itself or be ferried up to the satellite using an orbital transfer vehicle, such as the Shuttle Expendable Rocket for Payload Augmentation (SHERPA) tug also being developed by AeroAstro.
In his talk, Jacobovits argued that an Escort satellite could easily pay for itself. He noted that the cost of a large GEO communications satellite, including launch, could run $400 million, while the spacecraft is expected to last 10 years. If Escort could spot a problem that, if corrected by ground controllers, preserves a year of the spacecraft’s life, it represents a savings of $40 million—far more than the cost of an Escort microsatellite, he said. Jacobovits’ economics are a bit suspect: in today’s depressed commercial market, a satellite and launch can likely be obtained for $200 million or less, while spacecraft are expected to last 15 years, reducing one year’s savings to about $13 million. If, though, the costs to build and deploy Escort can be brought down below this level, it could become an attractive option, if not for satellite operators, then for the insurers who have suffered major losses in recent years because of on-orbit satellite failures.
While Jacobovits didn’t discuss it, Escort could have other applications as well. AeroAstro’s brochure about Escort mentions a number of non-commercial applications, such as “monitor space around a large satellite to detect attacks” and “stealthily attack to permanently or temporarily disable a large satellite.” Escort is also designed to be launched by RASCAL, a small satellite launch system that Space Launch Corporation is developing for DARPA.
Inspection microsatellites are also attracting the attention of universities. Michael Swartwout of Washington University in St. Louis described Bandit, a program he and his students are pursing. Bandit is a one-kilogram satellite that would be deployed from a larger microsatellite, Akoya. Bandit would autonomously maneuver away from Akoya and later rendezvous and redock. The project’s web site describes Bandit as a “flying camera” designed to operate for just a few hours. Akoya is one of a dozen competitors in the University Nanosat-3 project, jointly conducted by the Air Force, NASA, and the AIAA. One satellite will be selected for launch at some point after 2005.
The next step up from inspecting satellites is to service them, either simply refueling or repairing and upgrading whole satellite subsystems. The concept has attracted a fair deal of attention, but to date there have been few cases of it in action, with the shuttle servicing of the Hubble Space Telescope the best-known example. Several proposals using small satellites might prove the viability of satellite servicing, however.
DARPA is currently developing one prototype for a serviceable satellite system, called Orbital Express. The project consists of two spacecraft: a client spacecraft dubbed NextSat and the Autonomous Space Transport Robotic Operations (ASTRO) servicer. The spacecraft will test autonomous rendezvous, docking, and propellant transfer technologies. The ultimate goal of Orbital Express, according to Sanj Sivapiragasam of SRS Technologies, a support contractor for DARPA who discussed the project at the Utah State conference, is to develop a non-proprietary satellite-to-satellite interface standard, as well as determine how affordable on-orbit servicing can be. The $112-million project is scheduled for launch in March 2006 as a secondary payload on an Atlas 5.
Projects like Orbital Express require that the client spacecraft have a standard interface for docking and servicing, meaning that existing spacecraft, as well as those scheduled for launch in the near future, cannot be serviced by spacecraft like ASTRO. However, there have been recent proposals for spacecraft that could service existing spacecraft without the need for docking interfaces. A year ago a new company, Orbital Recovery Corporation, announced the Geosynch Spacecraft Life Extension System (SLES). The idea behind SLES is that most GEO communications satellites end their lives because they run out of propellant to maintain their orbit, not because of hardware component failures. The SLES, weighing 500 to 800 kilograms, would launch as a secondary payload on an Ariane 5 and fly to a satellite in GEO that is nearing the end of its operational lifetime. The SLES would attach to the satellite’s apogee kick motor, a strong, stable attachment point found on nearly every GEO satellite, and take over the propulsion, navigation, and guidance for the satellite.
Orbital Recovery Corporation says it has identified “more than 40” GEO satellites that would be candidates for SLES, although the company has not announced any specific customers yet. Recently, the company has proposed using SLES to change the orbit of the Hubble Space Telescope, either boosting it into a higher orbit or changing its orbital plane to bring it to the International Space Station for further servicing. “This is not a technology that is beyond our grasp requiring hundreds of millions of dollars to develop,” writes Dennis Wingo, chief technical officer at Orbital Recovery. The first SLES launch is planned for 2005, and a SLES mission to Hubble could be ready in 2006, according to the company.
Other companies are also investigating similar concepts. MD Robotics, a Canadian company best known for the shuttle’s Canadarm robotic arm, is studying a concept presented at the Utah State conference called the Space On-orbit Servicing System (SOSS). The proposal is remarkably similar to what Orbital Recovery is developing: a spacecraft that would dock to the apogee kick motor of existing GEO satellites primarily to support spacecraft that have depleted their onboard propellant supplies. Unlike some other concepts, SOSS would be guided to its target spacecraft manually, rather than autonomously, in order to lower the overall cost of the system. The project appeared to be in the earliest study phases, although MD Robotics is gaining experience in on-orbit servicing as a member of the Boeing-led Orbital Express team.
How many of these proposed concepts actually fly remains unknown: while some, like Orbital Express, are fully funded, others are clearly looking for government and/or commercial customers and contracts. However, there is a justifiable need by both militaries and companies for satellites that can inspect and service other spacecraft, a need currently unfulfilled. Small satellites, given their size, cost, and schedule attributes, may be uniquely suited to carrying out many of these missions. It is a golden opportunity to get small satellites out of the lab and into orbit.